1. Field of the Invention
The present invention relates to refrigeration systems. More particularly the present invention relates to refrigeration systems wherein a liquid refrigerant is subcooled in a vapor condensing economizer.
2. Description of the Prior Art
Refrigeration systems of the vapor compression type typically employ a compressor to increase the temperature and pressure of a gaseous refrigerant. Connected thereto is a condenser wherein gaseous refrigerant is cooled so that it changes state to a liquid refrigerant. Thereafter the refrigerant may be subcooled in a vapor compressing economizer wherein part of the refrigerant is vaporized absorbing heat from the remaining liquid refrigerant. In that type of economizer the vaporized refrigerant is drawn from the economizer into the compressor for recycling through the condenser. The economizer consists of a chamber or tank connected in the system to receive liquid refrigerant from the condenser and to pass liquid refrigerant to the evaporator. The chamber is also connected to the second or subsequent stage of a multi-stage compressor to extract vaporized or gaseous refrigerant from the chamber. The chamber is thus maintained at intermediate pressure level between the condenser and the evaporator. When the liquid refrigerant enters the chamber from the condenser the drop in pressure causes some of the refrigerant to flash to a vapor. The heat of vaporization required to flash the refrigerant is extracted from the remaining liquid refrigerant subcooling same. This subcooling of the liquid refrigerant produces an overall improvement in the efficiency of the system. The liquid refrigerant remaining in the economizer, which has now been subcooled passes on to the evaporator or chiller. In the chiller, the refrigerant is evaporated and drawn into the first stage of the compressor to complete the cycle. In the above described refrigeration system it is necessary that the compressor be a multistage compressor such that the flashed refrigerant from the economizer may be drawn into the compressor between the stages allowing the economizer to be at an intermediate pressure to the condenser and the chiller.
It is also known to use vapor compression economizers with a centrifugal compressor having a combination impeller blade such that the flashed gas from the economizer may enter the centrifugal compressor in the middle of the blade thereby creating within a single compressor two separate pressure levels. In addition vapor compression economizers have utilized a single stage compressor with appropriate valving arrangements to allow liquid refrigerant to flow from the condenser to the economizer wherein gaseous refrigerant is withdrawn by the compressor from the economizer until such time as the economizer temperature reaches the desired level. At such time a valve opens allowing the refrigerant to be drawn into the chiller and the valving allows the compressor to remove the flashed refrigerant gas from the chiller. The compressor runs continuously, however, the suction line to the compressor is cycled alternately between the economizer and the chiller such that the compressor is always withdrawing refrigerant from either the economizer or the chiller and such that the refrigerant passing from the economizer to the chiller is always at the desired temperature.
Prior refrigeration systems utilizing a vapor compressing economizer have required a multiple stage compressor to provide varying pressure levels for the flashing to occur. Refrigeration systems with one single stage compressor have previously not been adaptable for retrofit machinery to provide the flash economizing steps since the pressure differential required has not been obtainable. The refrigeration system described hereafter is adaptable to be retrofitted to a single stage centrifugal compressor without the addition of complicated valving or of a second compressor or a second compressor stage to recompress the flashed gas from the flash economizer.